I am still reading The Magician King as my novel.  I have read a couple new chapters, and the plot has really continued.  It continued with Quentin and Julia going to the After Island after changing their route instead of going back to their Fillory kingdom.  They were searching for the magical key that was believed to be on one of the Outer Islands.  But they didn't really know what it was for or what it did.  But they went in search of it anyways.

When they did find the key, Quentin turned it in a random part of the air, and he and Julia were suddenly transported magically back to Earth, specifically in front of the house of Quentin's parents.  Now they are going on a journey to try to get back to Fillory and return to their positions of king and queen, while there are actually two kings and 2 queens.  Now they have to use Julia's resources on Earth to survive until they can get back to their kingdom, and must rely on each other's magic abilities and each other as old friends to get through this new adventure.  But they will have to fight enemies, and each other's old feelings from their pasts, to conquer their new quest and return to their new home.